On Tue, 2024-09-10 at 11:33 +0200, Paolo Bonzini wrote:
> > But actually, I wonder if we need to remove the KVM_BUG_ON(). I think if you
> > did
> > a KVM_PRE_FAULT_MEMORY and then deleted the memslot you could hit it?
>
> I think all paths to handle_removed_pt() are safe:
>
> __tdp_mmu_zap_root
> tdp_mmu_zap_root
> kvm_tdp_mmu_zap_all
> kvm_arch_flush_shadow_all
> kvm_flush_shadow_all
> kvm_destroy_vm (*)
> kvm_mmu_notifier_release (*)
> kvm_tdp_mmu_zap_invalidated_roots
> kvm_mmu_zap_all_fast (**)
> kvm_tdp_mmu_zap_sp
> kvm_recover_nx_huge_pages (***)
But not all paths to remove_external_spte():
kvm_arch_flush_shadow_memslot()
kvm_mmu_zap_memslot_leafs()
kvm_tdp_mmu_unmap_gfn_range()
tdp_mmu_zap_leafs()
tdp_mmu_iter_set_spte()
tdp_mmu_set_spte()
remove_external_spte()
tdx_sept_remove_private_spte()
But we can probably keep the warning if we prevent KVM_PRE_FAULT_MEMORY as you
pointed earlier. I didn't see that that kvm->arch.pre_fault_allowed got added.
